Class 7 Science chapter 16 NCERT Solutions
Chapter 16: WATER: A PRECIOUS RESOURCE
N C E R T Textbook Questions Solved
1. Mark ‘T’ if the statement is true and ‘F’ if it is false:
a. The freshwater stored in the ground is much more than that present in the rivers and lakes of the world. (T/F)
b. Water shortage is a problem faced only by people living in rural areas. (T/F)
c. Water from rivers is the only source for irrigation in the fields. (T/F)
d. Rain is the ultimate source of water. (T/F)
Answers: a. T b. F c. F d. T
2. Explain how groundwater is recharged.
Answers: The groundwater gets recharged through the process of infiltration. In infiltration, water seeps into the ground through the particles of soils and empty spaces and cracks of the earth under the lakes and ponds
3. There are ten tube wells in a lane of fifty houses. What could be the long-term impact on the water table?
Answers: The effect on the water table depends on the amount of water being used in any area and no refilling of groundwater. If only some families share a tube well, the water used for daily domestic purposes would not affect the water table. But if there is a shortage of rain, the water used by the family would not be replenished and the water table would fall down.
4. You have been asked to maintain a garden. How will you minimise the use of water?
Answers: We can use the method of drip irrigation to reduce the wastage of water. In this method, we would lay downpipes at the base of plants. Also, we would make sure that there should be no leakage in pipes. We can also harvest the rainwater and with the help of pipes, we can put it over the base of the plants.
5. Explain the factors responsible for the depletion of the water table.
Answers: Some various factors responsible for the depletion of the water table are as follows:
(i) Increasing population
- The increasing number of the population needs more and more water for its day to day activities.
- Due to increasing population, we are consuming more groundwater and on the other hand, we are allowing less rainwater to seep into the ground by cutting trees, making cemented roads and floors out of the houses, etc.
- This leads to depletion of the water table.
(ii) Increasing industries
- Everything made in industries needs water at some stage during its production.
- As the population is increasing, the demands of various products are also increasing.
- Due to the demands of products, the number of industries is also increasing.
- For water, these industries depend upon the groundwater.
- This dependency also increases the stress on underground water.
- This results in depletion of the water table.
(iii) Agricultural activities
- The growing of various crops in agriculture requires a lot of water for irrigation.
- In times of irregular rainfall, the farmers have to use groundwater for irrigation.
- More and more food has to be grown for increasing population the use of groundwater for agriculture is increasing.
- This leads to depletion of water table too.
6. Fill in the blanks with the appropriate answers:
a. People obtain groundwater through_____ and ________.
b. Three forms of water are _______, _____ and ________.
c. The water-bearing layer of the earth is ________.
d. The process of water seepage into the ground is called ________.
Answer:
a. wells, hand pumps.
b. liquid, gas and solid
c. aquifer
d. infiltration
7. Which one of the following is not responsible for water shortage?
i. The rapid growth of industries.
ii. Increasing population.
iii. Heavy rainfall.
iv. Mismanagement of water resources
Answer: iii. heavy rainfall
8. Choose the correct option. The total water.
i. in the lakes and rivers of the world remains constant.
ii. under the ground remains constant.
iii. in the seas and oceans of the world remains constant.
iv. of the world remains constant.
Answer: iv. of the world remains constant.
9. Make a sketch showing groundwater and water table. Label it.
Answer:
Additional Questions Objective Questions
A. Indicate ‘true’ and ‘false’ among the following sentences:
1. Water availability includes all the three; water stress, water deficits and water crisis.
2. One of the main reasons for water shortage is the rapid growth of industries.
3. The people in the village suffer because they spend hours in fetching water from distant places due to scarcity of water.
4. In some places, there is an actual shortage of water during winter days.
Answer: 1. F, 2 T., 3. T, 4. F
B. Fill in the blanks:
1. The water found below the water table is called_____.
2. The rainwater can be used to_____ the groundwater.
3. Leaving the tap open is a source of _______.
4. Three forms of water are _____, _____ and _____.
5. _______ of buildings is one of the ways to use water economically.
6. ‘Every _______ counts’ is a slogan related to the importance of water.
7. Any type of _______ in taps are also a source of water wastage.
8. Rajasthan is a cold and dry place because of the _______ rainfall.
Answer:
1. groundwater,
2. recharge,
3. water wastage,
4. solid, liquid and gas
5. Proper Construction,
6. drop,
7. leakage, 8. scanty